Two devices transmit signals to each other through a cable disposed between these devices. However, in recent years, since the transmission amount of the signals increases substantially, high-frequency signals are used in the signal transmission. Moreover, two adjacent wires in the cable are quite close, so the transmission of the high-frequency signal is susceptible to an interference problem, producing a crosstalk phenomenon on the high-frequency signal, causing errors in the signal transmission and reducing the quality of transmission.
In order to solve the interference problem generated by the high-frequency signal, the wire for transmitting information coated with a metal shielding structure is designed to solve the high-frequency interference problem. The shielding structure may be fixed to the wire in many ways. When the shielding components coated on the exterior of the wires are fixed in a spiral longitudinal winding manner, gaps are easily formed between the shielding components or the shielding components have different thicknesses across the surface of the wire, which can easily affect the wire and cause inconsistent impedances, resulting in a an increase in insertion loss, and thus reducing the efficiency of signal transmission.
In existing art, with reference to FIG. 9, U.S. Pat. No. 8,653,373 discloses a shielded cable structure A. The cable structure A includes a pair of wires B, a first shielding tape C and a second shielding tape D. Each wire B includes a core wire B1 and an insulator B2. The core wire B1 is coated by the insulator B2. The first shielding tape C includes a plastic tape C1 and a metal foil C2. The plastic tape C1 and the metal foil C2 are attached to each other. The second shielding tape D includes a plastic tape D1 and a metal foil D2. The plastic tape D1 and the metal foil D2 are attached to each other. These wires B are arranged in parallel. The first shielding tape C is secured to the surfaces of these wires B in a spiral winding manner in a direction in which these wires B extend longitudinally. Adjacent parts of the wound first shielding tape C overlap each other to form an overlap portion C3 and a step portion C4. The second shielding tape D is secured to the surface of the first shielding tape C in a spiral winding manner in the direction in which these wires B extend longitudinally, and the winding direction of the first shielding tape C is different from that of the second shielding tape D. Adjacent parts of the wound second shielding tape D overlap each other to form an overlap portion D3 and a step portion D4. By doubly coating the wires B with the first shielding tape C and the second shielding tape D, a better electromagnetic shielding effect is expected.
However, the outer surfaces of the wires B are coated by the first shielding tape C and the second shielding tape D in a multi-layer manner, the spiral winding manner makes these first shielding tapes to form overlapping structures having different layers, which vary constantly in the direction in which these wires B extend longitudinally. The first shielding tape C and the second shielding tape D form an overlapping structure having three layers and an overlapping structure having four layers on the outer surfaces of these wires which alternate. These overlapping structures easily cause the impedance values of the wires B to vary continuously, resulting in an increase of insertion loss, thereby affecting the quality and efficiency of signal transmission in the wires B.
The spiral winding manner of these shielding tapes disclosed by the related art still has a defect of inconsistent impedances, easily causing a loss in the signal transmission, unable to meet various industrial requirements. In order to maintain the quality of signal transmission in the cable, there is a tremendous need for an improved design for the cable.